1. Field of the Invention
This invention relates to a protocol converting apparatus suitable for use with a user terminal apparatus of a CAPTAIN (Character And Pattern Telephone Access Information Network) system and in which the character information of the NAPLPS (North American Presentation Level Protocol Syntax) system can be used by the CAPTAIN user terminal apparatus.
2. Description of the Prior Art
The videotex system can be regarded as a data communication system accompanied with a still image. This videotex system is particularly featured in that the existing telephone network line is used as a transmission line and that a home television receiver is used as a display apparatus. Further, since the videotex system is capable of interactive communication, the videotex system is expected to be used in a wide field of applications. At present, three standard systems of videotex systems, such as, CEPT (Committee European des Postes et Telephone), NAPLPS and CAPTAIN are available in European countries, North America and Japan.
The CAPTAIN system, which is the videotex system in Japan, will be described with reference to FIGS. 1 to 4.
According to the CAPTAIN system, fundamentally an alphanumeric character is used as a character and the information thereof is transmitted through a code system. To express a figure or pattern, a "photographic system" is used in which the pattern is expressed with high fidelity by a dot (picture element) pattern as shown in FIG. 1A. Since the CAPTAIN system adopts such a hybrid system, the CAPTAIN system does not require a high processing ability in a user terminal apparatus and can transmit a complex pattern with ease. On the other hand, the amount of information to be transmitted is so much that the transmission rate of the down-link from the CAPTAIN center to the user terminal is selected as 4800 bits/second and that the transmission rate of the up-link from the user terminal to the CAPTAIN center is selected as 75 bits/second.
In addition to the above mentioned picture display system, the CAPTAIN system is supported by a "geometric function" which displays the pattern by using dots, straight lines, arcs, polygons and the like as shown in FIG. 1B and a "mosaic function" which displays the pattern by combining mosaic pieces as shown in FIG. 1C.
The CAPTAIN system is fundamentally formed of an information center, a videotex communication network (telephone network) and a user terminal apparatus as shown in FIG. 2.
Roughly classified, there are known two kinds of information centers, for example, the CAPTAIN information center and a direct type information center DF. An information processing apparatus CAPF of the CAPTAIN information center accumulates picture information supplied from information providers and transmits them to the videotex network. In the direct type information center DF, the making, accumulation and transmission of a picture, the processing of data from a user terminal GT and so on are all carried out by the information provider. An indirect type information center IF and an information input center INC register the picture information to the CAPTAIN center and the accumulation and the transmission of such picture information are carried out by the CAPTAIN center.
Referring to FIG. 3, the user terminal apparatus GT includes a MODEM (modulator and demodulator) 2, which is connected through an input terminal 1 to a telephone network line (not shown), a computer (CPU) 3, which interprets the picture information from the MODEM 2 and a frame memory 4 in which the picture interpreted by the computer is stored. The picture stored in the frame memory 4 is supplied through a video signal generator 5 to a display 6 and is thereby displayed on the display 6.
The user terminal apparatus are classified into five ranks and the fundamental function, the standard function, the optional function and the like are standardized for each rank of the user terminal apparatus. Referring back to FIG. 2, when the user terminal apparatus GT is connected to the videotex communication network (telephone network line), terminal profile information indicative of the rank and the function of the user terminal itself is transmitted from the user terminal apparatus and a communication processing apparatus VCP in the videotex network carries out the protocol conversion on the basis of the terminal profile information.
The fundamental functions of the user terminal apparatus are indicated in the table 1 below.
TABLE 1 ______________________________________ Character information Photo- (including graphic mosaic Pattern Geometric Terminal Pattern information, Pattern Rank Apparatus information DRCS information) information ______________________________________ 1 Pattern available partly not terminal available available 2 Hybrid available available not terminal available 3 High available available not Density available Hybrid terminal 4 Command available available available terminal 5 High available available available Density Command terminal ______________________________________
For a user terminal apparatus of the ranks 1, 2 and 4, a home television receiver can be used and the number of the picture elements forming a display screen amounts to 192 dots in the longitudinal direction and 248 dots in the lateral direction. On the other hand, for a high density terminal apparatus of the ranks 3 and 5, twice as many dots, that is, picture elements can be displayed (384 dots in the longitudinal direction and 496 dots in the lateral direction) compared to the normal user terminal apparatus of the ranks 1, 2 and 4. The high density user terminal, however, requires a special display.
As illustrated in FIG. 4, the video or display screen of the display 6 (FIG. 3) is of a multi-frame arrangement in which a plurality of display screens are superposed. Fundamentally, the above mentioned display screen is formed of three frames: a character information frame 7C, which displays a character, a mosaic pattern and DRCS (Dynamically Redefinable Character Set) information, a geometric information frame 7G and a photographic information frame 7P. The priority of their display is also in accordance with this order. The geometric information frame 7G is the dot unit coloring system frame, while the character information frame 7C and the photographic information frame 7P are each block coloring system frames.
Information that can be expressed by the CAPTAIN system is indicated in the following table 2.
TABLE 2 ______________________________________ Data Syntax CAPTAIN Items Japan ______________________________________ Main Display Function Alphaphotographic Character/Symbol Alphabets, Numerals, Symbols Display Function Japanese Syllabary, Japanese Cursive Syllabary, Chinese character Pattern Display Function Photographic YES (CAPTAIN system) Geometric YES (based on NAPLPS system) Mosaic Based on CEPT mosaic & mosaic special to CAPTAIN Special Pattern YES (special to CAPTAIN) (DRCS) Standard Coloring Unit character/mosaic character unit block coloring Geometric Dot coloring Photographic Block (4 .times. 4 dots) Number of display Standard Characters 15 columns .times. 8 rows (Chinese character) 31 columns .times. 16 rows (English letters, numerals and Japanese Cursive Syllabary) Number of colors 16 colors displayed simultaneously ______________________________________
Various kinds of information in the CAPTAIN system are transmitted through the following 4 code systems.
(1) Code mode code system PA1 (2) Transparent mode code system PA1 (3) Melody mode code system PA1 (4) Message mode code system PA1 (a) Character code set PA1 (b) Mosaic set PA1 (c) DRCS PA1 (d) PDI (Picture Description Instruction) set PA1 (e) Others PA1 (a) receiving means for receiving said first picture information; PA1 (b) separating means for separating said first picture information into character information and graphic information, said character information having position data indicating the display position by row and column of said character information; PA1 (c) position data converting means for converting the position data of said character information from said separating means into new position data for a user terminal of said second videotex standard, said position data converting means further including: PA1 (d) access code generating means for generating a next page access code in response to the change frame signal; PA1 (e) discriminating means for discriminating the signal from the user terminal of said second videotex standard generated by the operation of a next page access key therein and for generating an output signal in response thereto; PA1 (f) memory means responsive to both the discriminating means output signal and the change frame signal for storing the character information; and PA1 (g) transmitting means connected to the memory means for transmitting at least the character information together with the new position data, wherein said memory means stores the overflow character information in response to the change frame signal, the next page access code generated by said access code generating means is transmitted to said user terminal of the second videotex standard, and the character information stored in said memory is read out from said memory in response to the output signal of the discriminating means and supplied to said transmitting means.
Of these code systems (1) to (4), the former two code systems (1) and (2) are displayed on the afore-mentioned respective frames. The respective modes are changed-over by using a DI code of one byte. The DI codes indicating the code mode and the transparent mode are DI (C) and DI (T), respectively.
In the code mode code system of the CAPTAIN system, there are used the following code sets and others.
The character code set consists of Chinese character set such as Chinese characters according to JIS C6226 and the like, English letter and numeral set indicating English letters and numerals and Japanese Syllabary set indicating the Japanese Syllabary according to JIS C6200. The Chinese character set uses a two-byte system code.
The 8-unit code can express 256 kinds of codes at maximum so that the CAPTAIN system uses the codes extended in accordance with ISO (International Organization for Standardization) standard 2022.
The In-Use-Table used to extend the codes as described above is formed of 16 rows and 16 columns and the 16 columns are separated into 4 sets of the CO (0th to first columns), GL (second to seventh columns), C1 (eighth to ninth columns) and GR (tenth to fifteenth columns). In the GL and GR of the above mentioned In-Use-Table, of the G0, G1, G2 and G3 sets which are defined as the graphic sets, various kinds of code sets, which are prepared as the graphic repertory, are designated into any one of the 4 sets of G0 to G3. Further, the code sets designated in the G0 to G3 sets are invoked to the GL set or GR set on the In-Use-Table. In this case, the control codes are set in the C0 and C1 sets on the In-Use-Table.
The PDI is based on the NAPLPS which is the videotex system used in the North America and used to describe the pattern by using geometrical elements and coordinate points. As the fundamental patterns, there are provided a POINT, a LINE, an ARC, a RECTANGLE and a POLYGON.
According to the PDI set, one geometric figure is expressed by the combination of the operator code and the operand. The operator code is mainly used to designate the pattern element, while the operand is used to designate the coordinate point. The control command of the PDI set is used to select the color for the geometrical pattern.
In the transparent mode as earlier described, the information is transmitted as the unit of PDU (photographic data unit). The PDU includes one-bit photo-operator code and a photo-operand and the operand portion is formed of a parameter and a data. The photo operator code is a code to identify what the PDU data means and expresses the scanning range, the existence of the data compression, the coloring and the like. The parameter is the portion which supplements the operator code and the code of one to several bytes to describe the data indication coordinate and the details of the data content.
The NAPLPS system uses an alphanumeric as the character and the pattern is fundamentally expressed by using the afore-mentioned PDI and according to the "geometric system" shown in FIG. 1B. The NAPLPS system has the mosaic function and the independent DRSC function. In the NAPLPS system, the transmission rate of the down-link is selected as 1200 bits/second and the transmission rate of the up-link is 150 bits/second.
In Japan, independently of the public type CAPTAIN system, the NAPLPS system is used as a local area information system and an industrial information system.
The following table 3 indicates the information that can be expressed by the NAPLPS system.
TABLE 3 ______________________________________ Data Syntax NAPLPS Items North America ______________________________________ Main Display Function Alphageometric Character/Symbol Display Alphabets, Numerals and Function Symbols Pattern Display Function Photographic NO (Substituted by incremental point) Geometric YES (NAPLPS system) Mosaic Part of CEPT mosaic Special Pattern YES (special to NAPLPS) (DRCS) Standard Coloring Unit character/mosaic Character unit block coloring Geometric Dot coloring Photographic Number of Display Standard Characters 40 columns .times. 20 rows Number of colors 16 colors displayed simultaneously ______________________________________
Since the CAPTAIN and the NAPLPS are different systems, even if the information system of the NAPLPS system exists in Japan as described before, it is not possible to make an access of the NAPLPS information center (data base) using a CAPTAIN user terminal.
The character display ability of the NAPLPS system exceeds the CAPTAIN system with respect to any one of the number of rows and the number of columns. Accordingly, even when the access is made possible by the protocol conversion, an overflow condition of the characters to be displayed occurs so that one portion of the information will be dropped.